ASA 125th Meeting Ottawa 1993 May

5pSP8. Influence of dynamic spectral information on rate-dependent vowel perception.

Terry L. Gottfried

Susanne K. Triesch

Dept. of Psychol., Lawrence Univ., Appleton, WI 54912

Earlier research has shown that listeners adjust their identification of spectrally adjacent tense and lax vowels according to the speaking rate of the surrounding sentence. This study attempted to determine whether these rate effects could be reduced if test stimuli more closely resembled natural speech. Two synthetic /(ae ligature)/--/(eh)/ series were created: (1) covarying F1 and F2 with syllable duration (i.e., stimuli with more /(ae ligature)/-like formants were also longer in duration); (2) covarying formant frequencies with syllable duration and with formant frequency contours (i.e., stimuli with more /(ae ligature)/-like formants and duration had more symmetrical formant contours.) Stimuli from these series were embedded in fast and slow sentence contexts. In series (1), listeners identified more stimuli as /(ae ligature)/ in fast sentences, showing rate-dependent perception of this tense-lax contrast, replicating Gottfried et al. [Phonetica 47, 155--172 (1990)]. However, in series (2) (with appropriate formant contours---symmetrical for /(ae ligature)/ and longer offglide for /(eh)/), listeners showed no significant effect of rate. These results suggest that sentence rate may primarily affect vowel identification when important dynamic acoustic information is absent from the syllable itself.